Optical fiber connectors are used to optically couple one optical fiber to another optical fiber, or an optical fiber to optical devices such as LEDs, lasers or detectors. Such connectors form an essential part of substantially any optical fiber communications system, and the industry has expended a substantial effort on connector development.
The art knows a variety of connector types, including the so-called bi-conic connector (U.S. Pat. No. 4,107,242, co-assigned with this). For a discussion of optical fiber connectors, see, for instance, Optical Fiber Telecommunication, S. E. Miller and A. G. Chynoweth, editors, Academic Press (1979), especially pp. 483-497. One of the known connector types comprises two basically cylindrical fiber terminus pieces and mechanical means for maintaining the terminus pieces in substantially coaxial relationship, with the abutting surfaces of the terminus pieces substantially contacting. U.S. patent application Ser. No. 527,341, filed Aug. 29, 1983, and co-assigned with this, is an example of a connector of this type. Other examples are U.S. Pat. No. 4,140,365, and U.S. Pat. No. 4,283,125.
Connectors of this type, to be referred to herein as "ferrule-type" connectors, rely on the alignment of the outside surface of the terminus pieces to provide fiber alignment. For this approach to be satisfactory, it is obviously required that the fiber-receiving capillary bore of a terminus piece is concentric with the outer cylinder surface of the terminus piece. Furthermore, it requires that the optical fiber be flush with the mating end face of the terminus piece, and that the two mating end faces in a connector be normal to the fiber axis, to within quite close tolerances. Substantial deviations from these conditions tend to result in added signal loss. U.S. Pat. No. 4,221,461, co-assigned with this, discloses application of a compliant coating to the end face of a fiber terminus piece of a connector.
Not only does an optical fiber connector have to maintain the optical fiber ends coaxially aligned, it is also required to maintain the fiber ends in fixed longitudinal relationship, typically contacting or very nearly so, in the latter case often with some index-matching material between the fiber ends. This relationship has to be maintained for all rated longitudinal loads.
Optical fiber cables typically comprise strength members, e.g., KEVLAR (an aromatic polyimid) fibers, which are intended to be the primary load-bearing elements in case of longitudinal loading. Optical fiber connectors thus advantageously comprise means for transmitting longitudinal stress between the strength members of the joined optical cables. Such means are disclosed, for instance, in U.S. Pat. No. 4,283,125.
Other desirable characteristics of an optical fiber connector, including a connector of the ferrule-type, are simple construction and, therefore, low price, as well as small size, low loss, short assembly time, environmental stability, and versatility of design, e.g., adaptability of the basic design for simplex (one fiber) duplex (two fibers), or two or more fiber (multiplex) connectors. This application discloses a fiber connector possessing these desirable characteristics.